All-solid-state lithium battery with high capacity enabled by a new way of composite cathode design

A simple way to assemble an all-solid-state lithium-ion battery with ultrahigh surface capacity and energy density was established. Polyethylene oxide-based solid-state electrolyte was prepared via solution method and nano-SiO2 was added into the electrolyte to increase the conductivity. Thick compact LiFePO4 pellet infused with dry polymer electrolyte was used as the composite cathode in the all-solid-state lithium battery. The compact composite cathode not only showed large ionic and electronic conductivity, but also provided sufficient “free space” to compensate the volumetric change of the active materials during cycling. The all-solid-state lithium battery (composite cathode/dry polymer electrolyte/Li) was cycled at a constant current density of 200 μA/cm2 at 60 °C. A maximum discharge specific capacity of 157 mAh/g was achieved and the surface capacity reached 15 mAh/cm2, which was of critical significance for all-solid-state lithium batteries. Good capacity retention was achieved after 10 cycles and great rate performance was obtained. Even at a current density of 1000 μA/cm2, the battery delivered a specific discharge capacity of 71 mAh/g, corresponding to a surface capacity of 6 mAh/cm2. The experimental data demonstrated that the composite cathode was a promising design in high-performance bulk-type all-solid-state lithium batteries.